One of the major problems in the lives of cirrhotic patients is the inability to sleep coupled with daytime fatigue. We have completed a study where cirrhotic patients exhibited a striking alteration in the diurnal rhythm of plasma melatonin, which reflects the output of the "biological clock," or suprachiasmatic nucleus. The delay in the onset and peak levels of the nocturnal rise of the hormone is suggestive of a phase delay in circadian rhythmicity. We propose to study whether the rhythm of melatonin can be altered by exposure to bright light.